Elastix: generated output image doesn't align with applied and hardend transform

I’m quite new to slicer so maybe there‘s a very simple answer to my problem.

I’m currently using Elastix to registrate brain MRIs.
The genereated output volume looks perfectly fine but applying the transform to the original image and it’s segmentation it looks completely different from the output volume.

I already looked up the other topics and found out I need to harden the transform, but still, it doesn’t match.

Output volume

Original data moving-MRI before applying transform

Moving-MRI after applying transform and hardening transform

Thank you so much for your help!

I’m so sorry but I’m still looking for help. Could anyone possibly tell me what I’m doing wrong?

Thank you !